United States In cooperation with Department of Managing Degraded Agriculture United States Department of Forest Transportation Off-Highway Vehicle Trails Service Federal Highway in Wet, Unstable, and Technology & Administration Development Program United States Sensitive Environments Department of 2300 Recreation the Interior October 2002 0223-2821-MTDC National Park Service

OF TRAN T SP EN O M R T T R A T A I P O

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U N I A T C E I R D E ST M ATES OF A

Kevin G. Meyer, Environmental Specialist/Soil Scientist National Park Service, Alaska Support Office Rivers, Trails, and Conservation Assistance Program

USDA Forest Service Technology and Development Program Missoula, MT

2E22A68—NPS OHV Management

October 2002

The Forest Service, United States Department of Agriculture (USDA), has developed this information for the guidance of its employees, its contractors, and its cooperating Federal and State agencies, and is not responsible for the interpretation or use of this information by anyone except its own employees. The use of trade, firm, or corporation names in this document is for the information and convenience of the reader, and does not constitute an endorsement by the Department of any product or service to the exclusion of others that may be suitable.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, D.C. 20250–9410, or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer. i You can order a copy of this document using the order form on the FHWA’s Recreation Trails program Web site at: http://www.fhwa.dot.gov/environment/trailpub.htm

Fill out the order form and fax it to the distributor listed on the form. If you do not have Internet access, you can send a fax request to 202–366–3409, or request by mail from: USDOT, Federal Highway Administration Office of Human Environment, Room 3301 400 7th St. SW. Washington, DC 20590

Produced by: USDA FS, Missoula Technology and Development Center 5785 Hwy. 10 West Missoula, MT 59808-9361 Phone: 406–329–3978 Fax: 406–329–3719 E-mail: [email protected]

OF TRAN NT SP E O M R T T R A A T I P O

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This document was produced in cooperation with the U.S. Department of Transportation, Recreational Trails program of the Federal Highway Administration, and the U.S. Department of the Interior, National Park Service.

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof.

The contents of this report reflect the views of the contractor, who is responsible for the accuracy of the data presented herein. The contents do not necessarily reflect the official policy of the Department of Transportation.

This report does not constitute a standard, specification, or regulation. The United States Government does not endorse products or manufacturers. Trade or manufacturer’s names appear herein only because they are considered essential to the object of this document.

vi Acknowledgments

The author wishes to thank

Kevin Keeler and other staff from the Alaska Rivers, Trails, and Conservation Assistance program;

Brian Vachowski, Sara Lustgraaf, and Bert Lindler from the USDA Missoula Technology and Development Center;

Christopher Douwes from the USDOT Federal Highway Administration;

and the many OHV trail managers who are attempting to find ecologically sound solutions to OHV impacts.

ii Contents

Introduction ______1 Soil—The Stuff Under Foot, Hoof, and Wheel______2 Soils 101 ______2 Soil Characteristics as a Structural Component for Trails ______3 How Soils Are Degraded ______5 Surface Erosion, Surface Failure, and Trail Braiding ______6

Trail Management—Responding to Trail Degradation _____ 9 Management Components ______9 Trail Location Documentation ______9 Trail Condition Assessment ______9 Trail Improvement Prescriptions ______13 Trail Improvement Implementation ______14 Trail Maintenance and Monitoring ______15 Management Response to Severely Degraded Trails ______15 Trail Rerouting ______16 Seasonal or Type-of-Use Restrictions ______17 Controlled Use (Traffic Volume Restrictions) ______17 Trail Hardening ______18 Trail Closure ______31

Status of Research ______32

Summary ______33 Recommendations ______34 Research ______34 Funding ______34 Interagency Coordination ______34

References ______35

Appendix A—Subjective Evaluation of Off-Highway Vehicle Trail Treatment Options for Alaska______37

Appendix B—Installation Guide for Porous Pavement Panels as Trail-Hardening Materials for Off-Highway Vehicle Trails ______39

Appendix C—National Park Service Rivers, Trails, and Conservation Assistance Program Cooperative Research on Trail Hardening for Degraded Trails in Alaska ______47

Appendix D—Metric Conversions ______48

iii Introduction

nvironmental impacts associated with the degradation This document provides land managers and trail users with an of off-highway vehicle (OHV) trails have become a introduction to OHV trail degradation and outlines a framework serious concern in many regions. Where OHV trails for management responses. The information presented is based E indiscriminately cross alpine areas, wetlands, steep on work conducted by the author in southcentral and interior slopes,E and other areas with sensitive soil conditions, trails can Alaska, but it also applies to degraded trails in other parts of become rutted, mucky, and eroded. Such areas are referred the country. Some of the principles also apply to degraded to as degraded trail segments. Degraded trails develop when foot, mountain bike, and horse trails. The document presents trail use exceeds the trail’s natural carrying capacity. some fundamental concepts of soil and site characteristics, and the mechanics of trail degradation. It also offers inventory For land managers, degraded trails are a significant environ- methods to document trail conditions and prepare stabilization mental problem because of their direct effects on vegetation, “prescriptions.” In addition, it outlines a number of management soils, and site hydrology. In addition, degraded trails may have options including trail rerouting, seasonal and type-of-use re- indirect effects on wildlife, site esthetics, and other resource strictions, use-level restrictions, trail hardening, and trail closure. values. For trail users, degraded trails reduce the utility of trail systems and lead to a less enjoyable ride. Unfortunately, with increased use of backcountry resources by OHV enthusiasts and other trail users, the miles of degraded trails are increasing rapidly (figure 1).

The information provided in this report is intended to stimulate additional research and networking among trail managers, trail users, and the conservation community. Only through the cooperative efforts of a wide range of public and private trail advocates can the environmental and social conflicts associated with OHV use be resolved. We hope that future efforts will lead to the development of a widely applied set of best management practices for OHV trail management.

We have used English units of measure instead of Standard International (SI), or metric units, throughout this report. The products discussed in this report are manufactured using Figure 1—A degraded trail in interior Alaska. Heavy use has stripped English measurements and most trail workers are accustomed surface vegetation and exposed permafrost soils to accelerated melting, to English rather than metric units of measure. Appendix D resulting in muddy, rutted trail surfaces, erosion, and deep muck holes. includes conversions from English measurements to metric.

1 Soil—The Stuff Under Foot, Hoof, and Wheel

ost backcountry trails are constructed on native soils. A review of some basic concepts of soil and its engi- neering characteristics will help explain why trails M degrade, and why soils and physical site conditions areM important components in trail management.

Soils 101

Soil is unconsolidated material on the Earth’s surface. It is com- posed of mineral and organic particles, the voids surrounding the particles, and the water and air within the voids. The com- position of the particles and their relationship to the voids strongly affect the physical characteristics of soil. That compo- sition, called soil structure, describes the character of soil aggregates. These aggregates of individual soil grains form unique shapes depending on the soil’s origin and the surround- ing environmental conditions. The shapes of aggregates include granules, plates, prisms, columns, and blocks. The voids between the aggregates form passageways for air and gas exchange, as well as for water movement within the soil body.

The character of soil varies from place to place across the landscape. A soil’s mineral and organic content, structure, moisture content, depth to bedrock, ability to support vege- tation, and other characteristics vary, depending on the soil’s origin and the environment in which the soil is located. As a result, individual soil types cover the Earth’s surface like a mosaic. Five soil-forming factors control the character of a soil at any given location (U.S. Department of Agriculture 1993):

➣ Parent Material is the material in which a soil develops. Examples of mineral-based parent materials include alluvial deposits, weathered bedrock, glacial remnants, wind deposits, and marine sediments. Organic parent materials include leaf litter and decomposing wetland vegetation. The parent material influences the texture of the soil—the relative amounts of sand, silt, clay, and organic material that make up the finer components of the soil and the percentage of boulders, cobbles, and gravel that make up the larger components.

➣ Topography is where the soil is located on the landscape. It includes the elements of slope, aspect, elevation, and landscape position of the soil. Slope strongly influences the risk of erosion, aspect (relative sun exposure) influences daily temperature variations, and elevation influences climatic environment. Landscape position describes the soil’s location on the landscape—such as: ridgeline, alluvial terrace, highly dissected upland, foot slope, floodplain, and high terrace.

2 Soil—The Stuff Under Foot, Hoof, and Wheel

➣ Time is the period parent materials have been subject to ➣ Finely textured soils—those with high percentages of weathering and soil-forming processes. In general, the older organic matter, silt, and clay the soil, the greater the chemical and physical modification of the original parent material and the more developed a ➣ Coarsely textured soils—those with high percentages of soil’s internal structure. Through time, soils develop distinct sand and gravel layers. Soil scientists generally recognize four layers: ‘O’ for surface organic layers, ‘A’ for the organic-rich surface In general, the coarsely textured soils have good bearing mineral layers, ‘B’ for the weather-altered subsoil, and ‘C’ capacity. This is because of their large particle size, good for the unaffected parent material. drainage characteristics, and low shrink-swell potential. Conversely, finely textured soils generally have poor bearing ➣ Climate indicates the effect of local weather on soil devel- capacity because of their small particle size, poor drainage opment. Climate influences chemical weathering, soil characteristics, and a tendency to shrink or swell under different temperature, and soil moisture levels. Within a localized area, moisture conditions. Both classes of soils have moderate to topography moderates climate to some degree. poor cohesion, depending on other factors such as vegetation cover and roots that help hold individual soil particles in place. ➣ Organisms are the plants, animals, and humans that affect soil development. This includes effects from vegetation Soil moisture level measures the relative amount of water in growth, leaf litter accumulation, soil microorganisms, bur- soil pores. A soil’s texture controls the percentage of pores rowing animals, and human agriculture, recreation, and within a soil. Surprisingly, finely textured soils have more pore construction. Organisms can dramatically affect a soil’s space than coarsely textured soils. Finely textured soils can development. Vegetation enriches soils by contributing have up to 60 percent void space, while coarsely textured soils organic material and aiding in the development of internal typically have around 40 percent. soil structure. Unfortunately, many human activities have a disruptive effect on soil development. Soil moisture can range from bone dry to totally saturated. Because water acts as a lubricant for soil particles, the relative Starting with raw parent material, topography, time, climate, amount of water within a soil can dramatically affect its struc- and organisms work together to weather, mix, and transport tural stability. While coarsely textured soils tend to have good soil. Soil is continuously evolving and modifying its capacity bearing strength across a wide range of moisture conditions, to support plant, animal, and human use over time. finely textured soils have reduced bearing capacity as moisture levels increase. At saturation, when all soil voids are filled with water, finely textured soils typically have little bearing capacity. Finely textured soils store and retain water over long periods so their bearing capacity can be low for prolonged periods.

Soil’s Characteristics as a Structural Besides soil texture and soil moisture, other environmental and site factors contribute to a soil’s structural capability and Component for Trails suitability for trails. These include:

Unlike bedrock, asphalt or concrete, soil is an unconsolidated ➣ Soil temperature ➣ Depth to bedrock material composed of loosely bonded particles and the voids ➣ Type of surface cover ➣ Slope surrounding them. The lack of solid bonds between particles ➣ Root mass ➣ Landscape position means that soils are susceptible to impacts from trail use in a number of ways. These include crushing, lateral displacement, These factors largely control how well a soil will support surface and erosion. A soil’s ability as a structural component for trails traffic. These characteristics also provide insights on how soil is controlled by two factors, its bearing strength (its ability to should be managed and on the options that might be employed support a load without being deformed) and its cohesion (the to increase its suitability for use. Table 1 provides some general ability to resist displacement). Those abilities are primarily guidelines on broad categories of trail suitability based on controlled by two related factors: the relative size of soil particles these factors. The table segregates site characteristics into (soil texture) and the relative water content of the soil voids three classes of suitability for each soil factor: poorly suited (soil moisture level). (highly sensitive), limited suitability (moderately sensitive), and generally suitable (slightly sensitive). Soil texture is the relative amount of organic matter, gravel, sand, silt, and clay in a soil. In general, soil texture can be broken into two major classes:

3 Soil—The Stuff Under Foot, Hoof, and Wheel

The information in table 1 can help trail managers identify may require significant attention and a high level of manage- where they may have problems with existing or planned trail ment. Poorly suited sites should be avoided during new trail routes. For example, sites with all ‘generally suitable’ ratings construction. Existing trails with “poorly suited” ratings should shouldn’t pose any inordinate management or environmental be assessed for environmental impacts and evaluated for concerns; those with ‘limited suitability’ ratings may require relocation. some special attention; and those with ‘poorly suited’ ratings

Table 1—General guidelines on trail site suitability and sensitivity to impact.

S U I T A B I L I T Y / S E N S I T I V I T Y C L A S S Poorly suited Limited suitability Generally suitable Soil factor (highly sensitive) (moderately sensitive) (slightly sensitive)

Soil texture All organic soils; soils with an Silt greater than 70 percent or Soils with a high percentage organic surface layer thicker clay greater than 40 percent of gravel or rock in the sur- than 4 inches in the soil surface layer; sand face layer component is greater than 80 percent in the surface layer

Soil temperature Ice-rich permafrost is within Low ice permafrost within Deeply frozen soils (winter 40 inches of the surface; soils 40 inches of the surface activities) at or near freezing

Soil moisture Poorly or very poorly drained Somewhat poorly drained Well- and moderately well- soils; the water table is within soils; the water table is be- drained soils; the water table 12 inches of the surface; tween 12 and 24 inches of is deeper than 24 inches water is ponded at the surface; the surface below the surface soils are at or near saturation

Type of surface All wetland vegetation commu- cover nities; permafrost-influenced vegetation communities; alpine tundra communities

Root mass Fine, thin, poorly developed Root mass that is 2 to 6 Root mass is more than 6 root mass inches thick, primarily fine inches thick with a high roots percentage of woody roots

Soil depth — Less than 2 feet to bedrock More than 2 feet to bedrock

Slope Slopes steeper than 40 Slopes between 6 and 20 Slopes less than 6 percent percent if the slope length is percent (with appropriate (with appropriate water longer than 50 feet; slopes 20 water control) control) to 40 percent if the slope length is longer than 100 feet

Landscape position North-facing aspects in some Ridgelines (if shallow soils); South-facing aspects; gravel climatic conditions foot and toe slopes (if wet bars, terraces, and alluvial or there are seep zones); benches; outwash plains; floodplains (seasonal flood- alluvial fans (depending on ing); slopes (depending on slope) percent of slope, see above)

4 Soil—The Stuff Under Foot, Hoof, and Wheel

How Soils Are Degraded The most common example is when the passage of a wheeled vehicle forms ruts. The downward force of the wheel shears—or Trail use damages soils when the type and level of use exceed displaces—the soil beneath it, forcing the soil to bulge upward the soil’s capacity to resist impact. A soil’s capacity to resist beside the wheel. This process is illustrated in figure 2. The impact varies depending on textural class, moisture level, and shearing action destroys soil structure by crushing soil peds other environmental and site characteristics, but the processes (natural soil aggregates) and collapsing voids. Shearing is most by which soils are impacted are generally the same. Trail use likely to occur on finely textured soils under moist to saturated damages soils directly by mechanical impact from surface conditions. It is uncommon in coarse soils. traffic and indirectly by hydraulic modifications, soil transport, and deposition. Shearing action Direct mechanical impact has several components: abrasion, (soil-bearing capacity of an unconfined load) compaction, shearing, and displacement.

➣ Abrasion strips surface vegetation and roots.

➣ Compaction reduces soil voids and causes surface subsidence.

➣ Shearing is the destructive transfer of force through the soil.

➣ Displacement results in the mechanical movement of soil Ground particles. surface

Indirect impacts include hydraulic modifications, such as the disruption of surface water flow, reductions in infiltration and Shear force Shear force percolation, surface ponding, and the loss of water-holding capacity. Other indirect impacts include those associated with Figure 2—Diagram of shearing action. erosion—both the loss of soil particles by wind or water erosion and deposition of transported particles. An associated impact is the hydraulic pumping that occurs when a destructive flow Pumping action occurs when soils are saturated with water. of water is forced through a saturated soil. Saturated soils are most common in wetlands, but may occur on other sites during spring thaw, periods of high rainfall, or Both direct and indirect impacts degrade trail segments. The where water is ponded. Pumping occurs when the downward impacts generally occur in the following progression: pressure of a passing force—such as a vehicle wheel—forces water through soil voids and passages. When the pressure is Abrasive loss of protecting surface vegetation and root mass released, water rushes back into the vacuum. This process is (direct impact)

➣ ➣ ➣➣➣ illustrated in figure 3. The force of this rapid water flow erodes internal soil structure and clogs soil voids with displaced sedi- Compaction and surface subsidence (direct impact) ment. Pumping occurs within all soils, but is most damaging to finely textured soils because of their fragile internal structure. Hydraulic disruption (indirect impact) Shearing and pumping actions reduce soils to a structureless Breakdown of soil structure from shearing and pumping or “massive” condition. This condition is characterized by the (direct impact) loss of distinguishable soil structure and a reduction in pore space voids, and interped passages (the space between peds). Soil particle erosion and deposition (indirect impact) An example of soil in a massive state is a dried mud clod or an adobe brick. In a massive state, soils have significantly While most of the stages in this progression are familiar con- reduced infiltration rates, percolation, water storage capacity, cepts, the shearing and pumping components may not be as and gas exchange. This reduces a soil’s ability to support vege- familiar to some readers. tation growth, leads to surface ponding of water, and increases the soil’s sensitivity to additional impacts. Shearing describes a transfer of force through a soil. When an applied force exceeds the capacity of the soil body to absorb it, a portion of the soil body can be displaced along a shear plane—that place where soil particle cohesion is weakest. 5 Soil—The Stuff Under Foot, Hoof, and Wheel

The two degradation pathways are diagrammed in table 2. Pumping action (soil-bearing capacity of an unconfined load) Table 2—Trail degradation pathways. Both pathways of impact begin when: Direction of motion Surface vegetation and roots are stripped by surface traffic.

➣➣

Exposed soil is compacted and the trail surface Ground subsides relative to the adjacent surface. surface Compaction and subsidence destroy soil structure and disrupt internal drainage patterns.

➣

Rebound Impact follows one of two paths: (release)

➣ Compressional force ➣ (pump) Surface erosion Surface failure

➣➣➣➣ Figure 3—Diagram of pumping action. ➣➣➣➣ Exposed surface is Water collects on the eroded by wind scour or trail surface.

Water drains onto the Water pools in low areas. trail surface. Surface Erosion, Surface Failure, and Pooled water saturates Water is channeled the soil. Trail Braiding along the trail surface. Shearing and pumping Trail use has a predictable path of surface impact. The degree Water erodes damage the soil structure.

➣ of impact is modified only by the natural resilience of the soil the trail surface. and the intensity of trail use. In an ideal situation, a natural ➣ Muddy sections and balance is maintained between soil resilience and use, and Deep erosion ruts deep muck holes form. trail use occurs without significant degradation. However, on form. sites with wet, unstable, and sensitive soils, that equilibrium

➣ is easily upset. Even low levels of trail use can have significant environmental consequences. The impact continues: Trail segments develop rutted or muddy sections.

Typically, trail degradation follows one of two pathways: surface ➣ erosion or surface failure. Surface erosion occurs when wind Trails widen as users avoid degraded sections.

or water displaces exposed trail surfaces. This usually occurs ➣ ➣➣➣ on steep terrain or on sandy soils that are susceptible to wind erosion. Surface failure occurs when trail surfaces degrade Trail users abandon degraded sections. into muddy tracks with deep muck holes. This usually occurs on flat areas with organic or finely textured soils. Either pathway New routes are pioneered on adjacent soils. can lead to significant environmental impacts that are extremely difficult to stabilize or reverse. Without stabilization, a destruc- Vegetation and roots are stripped by traffic along tive cycle of degradation can begin that expands the impact the new route. to adjacent surfaces. That cycle begins with the widening of trail surfaces as users avoid degraded surfaces and expands Soil is compacted and the soil structure is destroyed, to the development of multiple parallel trails. leading to surface erosion and/or surface failure.

And so the cycle repeats itself.

6 Soil—The Stuff Under Foot, Hoof, and Wheel

The first consequences of pioneering a trail across a virgin landscape are the stripping of surface vegetation, the abrasion of roots, and the compaction of surface soil layers. These impacts destroy soil structure, reduce water infiltration, and break bonds between soil particles. Soil particles are more vulnerable to displacement and loss from wind or water erosion. Soil compaction also leads to surface subsidence—the lowering of the trail relative to the adjacent ground surface. Trails become entrenched. This lower surface intercepts and drains water from adjacent surfaces and channels that flow along the trail. This dramatically increases the risk of water erosion on sloped areas and the pooling of water in low-lying sections. As trail surfaces degrade due to rutting or the formation of muck holes, users widen the trail and seek new routes, usually on adjacent soils where environmental conditions are identical to the original impact site. As this new route degrades, it is abandoned. A third route is pioneered, and then a fourth—until finally the area is scarred with a number of routes in various stages of use and Figure 4b—Results are an adjacent degraded alignment and the abandonment. This condition is called trail braiding. Trail braiding development of a braided trail. significantly expands the environmental impacts of trail use. Trail braiding occurs because trail use levels repeatedly exceed the carrying capacity of soils to support that use. Figures 4a In braided trail sections, abandoned trail segments may slowly and 4b illustrate the process. recover from impact through natural revegetation. However, the impact has usually dramatically altered the site’s thermal, soil, and hydrologic characteristics. These changes affect the composition and structure of vegetation that can grow on the disturbed site. For example, a site that supported shrubs and grass before disturbance may only support sedges or other water-tolerant plants after disturbance. Abandoned routes may also recover enough to support subsequent trail use, but they are generally more sensitive to impact than virgin sites.

The impacts associated with braiding are a major concern for land managers because they dramatically increase the area of impacts associated with trail use (figure 5). Studies conducted in one area of Alaska documented that the average OHV trail had an impact area 34.6 feet wide (Connery 1984)—that’s four times the width necessary for a single OHV track. Using that average width (34.6 feet), each mile of trail affects 4.2 acres. A single-track trail (8 feet wide) of the same length would affect just 0.97 acre per mile. Braided trail sections more than 200 feet wide are not uncommon within Alaska. For resource man- Figure 4a—Ponded water in ruts and muck holes prompt riders to agers, the increase in area affected by braiding is significant in pioneer new routes in adjacent undisturbed areas. terms of resource destruction, habitat loss, and esthetics.

7 Soil—The Stuff Under Foot, Hoof, and Wheel

In Alaska, the cycle of degradation is well studied and docu- mented (Connery 1984; Connery, Meyers, and Beck 1985; Ahlstrand and Racine 1990, 1993; and Happe, Shea, and Loya 1998). Responding to the impact has been more difficult. The problem is also compounded by rapidly expanding OHV use and increased OHV trail mileage. One study conducted by the Bureau of Land Management documented a 76-percent increase in miles of trail from the early 1970s to the late 1990s (Muenster 2001). Significant increases have also been observed in many other areas of Alaska. These increases in trail mileage and their associated environmental impacts on soil, vegetation, habitat, and water resource values have given resource man- agers a legitimate reason to be concerned about the impacts associated with degraded OHV trails.

Figure 5—A braided trail in Alaska. More than a dozen separate routes have been pioneered in this section crossing a wetland. Note the wet trail conditions and numerous potholes. At this site, trail impacts affect an area more than 250 feet wide. Braiding significantly extends the area of impact by modifying vegetation cover, surface hydrology, and soil characteristics.

8 Trail Management—Responding to Trail Degradation

Mlanagement Components Table 3—Trail impact classes. Impact The task of trail management ranges from planning, designing, class Subclass Description and constructing trails to maintaining them. In an ideal world, every trail would have a formal, well thought-out management A 1 Minor loss of original surface vegetation plan and a staff dedicated to its implementation. Unfortunately, (over 80 percent remaining) that is not the case. In Alaska, the term ‘orphan trail’ has been 2 Moderate loss of original surface vege- coined to describe active trails that receive no management tation (40 to 80 percent remaining) oversight at all. Trail management should include elements from these five basic building blocks: B 3 Most original surface vegetation stripped away (less than 40 percent remaining) ➣ Trail location documentation 4Exposed roots on trail surface ➣ Trail condition assessment ➣ Trail improvement prescriptions C 5Almost total loss of root mass ➣ Trail improvement implementation 6 Only exposed mineral or organic soil ➣ Trail maintenance and monitoring at surface 7Erosive loss of less than 2 inches of soil, or compaction and subsidence less than 2 inches deep Trail Location Documentation D 8Erosive loss of 2 to 8 inches of soil, or Trail location documentation is plotting the location of the trail compaction and subsidence 2 to 8 in a geographic database. A simple sketch of a trail location inches deep on a U.S. Geological Survey topographic map is better than F 9Erosive loss of 9 to 16 inches of soil, or no location data, but documenting the alignment with a mapping- compaction and subsidence 9 to 16 grade global positioning system (GPS) unit is best. The GPS inches deep unit can record geographic coordinates of a trail alignment that can overlay digital topographic maps or be downloaded 10 Erosive loss of more than 16 inches of into a geographic information system (GIS). The GIS allows soil, or compaction and subsidence more than 16 inches deep trail locations to be plotted over other geographic databases such as land ownership, soils, and terrain. Accurate trail location 11 Trail segment intermittently passable information is also critical for obtaining a legal right-of-way during dry conditions easement for a trail alignment. 12 Trail segment impassable at all times

Trail Condition Assessment For quick assessments, trail segments can be classified using classes A to F. For more detailed assessments, the numeric Condition assessment is an inventory of the physical character subclass designators can be used. of a trail alignment. It documents conditions and problems and provides a baseline for monitoring changes over time. This assessment can be used to set priorities for trail prescription Trail segments with class A impacts have yet to experience mapping (next section) and provide general information for significant degradation. Class B segments are generally new future trail improvement work. trails or lightly traveled routes. Segments with class C impacts display the beginnings of detrimental impacts, but have not yet The assessment should evaluate the entire trail length, not just been seriously degraded. Monitoring these sites should be a problem sites. This ensures that the assessment will provide high priority. Segments with class D impacts display degradation a basis for evaluating condition trend during future monitoring due to poor site conditions or excessive use. Mitigation may be efforts. Condition assessments can be conducted with manual needed to stabilize impacts. Segments with class F impacts are data collection using a measuring wheel, tape measure, or seriously degraded trails, probably with significant environmental odometer in the traditional “trail log” approach. The author has impacts. These sites should receive a high level of management developed a simple alphanumeric system to classify individual attention. Methods to respond to the degradation of classes trail segment conditions (table 3). D and F trail segments are detailed later.

9 Trail Management—Responding to Trail Degradation

While table 3 presents a classification system for manual assess- software and equipment. The legend contains a fairly complete ment, a much more powerful and descriptive assessment can be list of trail condition attributes, and it can be used as the starting made by using a mapping-grade GPS receiver that attaches line, point to develop a customized legend appropriate for any specific point, and area descriptors with collected trail alignment coordi- trail system. When the data elements in table 4 are loaded nates. The author has developed a trail condition mapping legend into a menu-driven GPS mapping system, they can be collected (table 4) that can be used with standard mapping-grade GPS easily during trail condition mapping.

Table 4—Trail condition mapping legend (bold text identifies the more important data fields).

Feature element Menu selection options

LINE FEATURE

TRAIL SEGMENT Trail segment type Single track, double track, or multibraid 6 to 20, 21 to 40, 41 to 80, 81 to 160, 161 to 320, 321 to 480, wider (feet) than 480

Trail track type Main, secondary, abandoned, access, cutoff, spur

Trail surface grade Zero to 6, 7 to 20, 21 to 40, steeper than 40 (percent)

Side slope (percent) Less than 20, 21 to 60, 61 to 100, steeper than 100

Trail surface Vegetated, native organic, wetland vegetated, floating organic, native fine mineral, mixed fines and gravel, sand, gravel, cobble, imported gravel, gravel over geotextile, wood chips, timbers/planking, corduroy, paved, porous pavement panel, rock, water crossing, other

Trail impact rating None Loss of surface vegetation Exposed roots Less than 2 inches erosive loss or surface subsidence 2 to 8 inches erosive loss or surface subsidence 9 to 16 inches erosive loss or surface subsidence 17 to 32 inches erosive loss or surface subsidence 33 to 60 inches erosive loss or surface subsidence More than 60 inches erosive loss or surface subsidence

Mud-muck index None, muddy, extremely muddy, muck hole, multiple muck holes, seasonally impassable, impassable at all times

Trail drainage Well drained, moderately well drained, poorly drained, saturated, ponded, water running across surface

Stone hindrance None, less than 10, 11 to 25, 26 to 75, 76 to 100 (percent)

Track width (feet) One to 3, 4 to 6, 7 to 12, 13 to 20, 21 to 30, 31 to 40, 41 to 60, over 60

Vegetation stripping Single track, wheel track only, full width of trail

Type of use Multiuse, foot only, motorized only

Season of use Multiseason, winter only, thaw season only

ROAD SEGMENT Road type Access, primary, secondary, subdivision, unimproved, other

Road surface Paved, gravel, dirt

Road width (feet) 8 to 12, 13 to 16, 17 to 20, 21 to 30

LINE GENERIC Line type Text entry Continued —>

10 Trail Management—Responding to Trail Degradation

Table 4—continued (bold text identifies the more important data fields).

Feature element Menu selection options

POINT FEATURE

WATER MANAGEMENT Type Water bar, grade dip, rolling dip, round culvert, box culvert, open drain, sheet drain, check dam, ditch

Condition Serviceable, poor

Culvert size (inches) Numeric entry

STREAM CROSSING Type Unimproved ford, improved ford, bridge, culvert

Stream name Text entry

Stream width (feet) Numeric entry

Approximate flow Numeric entry (cubic feet per second)

PHOTO POINT Frame/reference No. Numeric entry

Bearing (degrees) Numeric entry

ANCHOR POINT Type Beginning, middle, intersection, angle, end

REFERENCE POINT Type Milepost, trailhead, trail marker, survey marker, property marker, road crossing, junction, gate or barrier, other

Mileage Numeric entry

POINTS OF INTEREST Type Scenic vista, pullout, shelter, campsite, cabin, structure, powerline, fence, staging area

HAZARD Type Text entry

SIGNS Type Informational, directional, regulatory, warning

Text Text entry

POINT GENERIC Type Text entry

AREA FEATURE

PARKING AREA

BRAIDED IMPACT AREA

GENERIC AREA

Figure 6 displays a GPS plot of a complex trail system with a detail can be extracted for every line segment, point, or area large number of braided trail segments. Note the highlighted feature displayed on the screen. The ‘Feature Properties’ box trail segment at the top of the image. The ‘Feature Properties’ shows the location, date of data acquisition, and precision of data frame to the right of the screen lists the characteristics of the data collected. that trail segment as it was mapped in the field. Similar data 11 Trail Management—Responding to Trail Degradation

Figure 6—This computer screen display shows the mapping legend for a complex trail system with a large number of braided trails. The feature properties (data box on the right) relate to the bolded trail segment at the top of the display.

Data collected with this level of sophistication should be down- evaluate trail performance across varying soils and landscape loaded into a GIS system. While a GIS requires a relatively high units, and plan future work. level of technical support, it can have tremendous payoffs for trail management. Once downloaded, the data can be subjected Based on the author’s experience and some limited contract to a wide variety of map and tabular analysis, including overlay work conducted by the Bureau of Land Management in Alaska, with other geographic information such as soils and terrain. about 8 miles of trail can be mapped per day by a two-person Attribute values can be used to generate trail segment impact crew mounted on OHVs using the GPS-based system. Produc- ratings and to identify critical problem areas. The length and tion rates vary depending on trail conditions, weather, access, area of trail segments can be calculated to help estimate miti- staff experience, and equipment performance. Office support gation and maintenance costs. When the condition inventory work is required in addition to the field work. Allow about twice is incorporated into a GIS, it provides a baseline of trail as much time in the office as in the field to set up equipment, conditions that can be used to plan and track monitoring efforts, load data dictionaries, download data, edit data, and integrate the data into a GIS. 12 Trail Management—Responding to Trail Degradation

Trail Improvement Prescriptions field inventory technique, prescription mapping requires expertise in trail planning, construction and maintenance, and knowledge Trail prescriptions focus on identifying locations for specific of the trail construction and maintenance resources that are treatment applications, such as surface improvements, ditches, available. brush control, water management, and water-crossing structures. Prescription mapping can be greatly assisted by GPS/GIS The crew preparing trail prescriptions needs to be knowledgeable technology. Table 5 is a prescription mapping legend developed of the treatments available for specific trail ailments. Unlike by the author. It identifies a wide range of treatments and can condition mapping, which requires just a basic knowledge of be adapted readily for use on any trail systems.

Table 5—Trail prescription mapping legend (bold text identifies the more important data fields).

Feature element Menu selection options

LINE FEATURE

TRAIL SEGMENT Trail type Active, inactive, new segment, access, water crossing, other

Surface treatment No treatment, light water management, heavy water management, grading/leveling, gravel cap, gravel/ geotextile, porous pavement, corduroy, turnpike, puncheon-boardwalk, abandon—no treatment, abandon with light rehabilitation, abandon with heavy rehabilitation

Gravel cap depth None, 2 to 4, 5 to 8, 9 to 12, 13 to 18, deeper than 18 (inches)

Trail width (feet) Numeric entry

Surface treatment priority High, medium, low

Ditching None, left (outbound), right (outbound), both

Ditching priority High, medium, low

Brush control None, left, right, both

Brushing priority High, medium, low

Root removal None required, required

Cut-and-fill section None, less than 15, 16 to 45, 46 to 100, more than 100 (percent side slope)

LINE GENERIC Type Text entry

POINT FEATURES

ANCHOR POINT Type Beginning, middle, intersection, angle, end

REFERENCE POINT Type Milepost, trailhead, trail marker, survey marker, gate or barrier, road crossing, fence crossing, other

Mileage Numeric entry

WATER MANAGEMENT Type Water bar, grade dip, rolling dip, culvert (diameter in inches, less than 8, 9 to 16, 17 to 36, larger than 36), check dam, open drain, other

WATER CROSSING Type (feet) Unimproved ford, improved ford, bridge (shorter than 12, 13 to 24, longer than 24) Continued —>

13 Trail Management—Responding to Trail Degradation

Table 5—continued (bold text identifies the more important data fields).

Feature element Menu selection options

POINT FEATURE (continued)

PHOTO POINT Reference number Numeric entry

Bearing Numeric entry

POINT-OF-INTEREST DEVELOPMENT Type Scenic vista, pullout, shelter, campsite, cabin

FIX HAZARD Type Tree removal, stump removal, rock removal, guardrail, fill hole, other

SIGN NEEDED Type Informational, directional, regulatory, warning

Text Text entry

SIDE SLOPE FEATURE Type Switchback center point, climbing turn center point

GRAVEL SOURCE

TIMBER SOURCE

STAGING AREA

POINT GENERIC

AREA FEATURE

GENERIC AREA

A prescription inventory collected with a GPS system provides Trail Improvement Implementation an excellent basis for cost and labor estimates, but it does not have the familiar ‘1+00’ trail log references typically associated Improvement implementation is planned trail maintenance, with trail inventory work. Therefore, ground location reference stabilization, or mitigation based on a trail improvement pre- points should be established before or during the inventory. scription. Improvement actions should be based on standard Markers every one-quarter mile—or every 1,000 feet—are not design specifications or commonly accepted management too close for detailed surveys. Measuring wheels and OHV practices. Commonly accepted practices are best described odometers are common measuring devices for establishing in the following Federal and private publications: approximate milepost locations. Labeled flagging, lath, or metal tags should be placed at these standardized reference points. Building Better Trails. 2001. International Mountain Bicycling The more permanent the markers, the better. Association, P.O. Box 7578, Boulder, CO 80306. Phone: 303– 545–9011; e-mail: [email protected]; Web site: http://www.imba. com. May be purchased both in HTML and PDF formats from the Web site or the IMBA office. 64 p. in printed book format.

14 Trail Management—Responding to Trail Degradation

Installation Guide for Porous Pavement Panels as Trail Periodic inspections also should be made of bridges, especially Hardening Materials for Off-Highway Vehicle Trails. 2001. after spring breakup or floods. Maintenance crews also should Kevin G. Meyer. USDI National Park Service—Rivers, Trails, report on problem areas and maintenance concerns. In many and Conservation Assistance Program Technical Note, 2525 cases, periodic, systematic maintenance can head off major Gambell St., Anchorage, AK 99503 (attached as appendix B). trail degradation.

Lightly on the Land—The SCA Trail Building and Mainte- Monitoring to detect changes in trail conditions, including a nance Manual. 1996. Robert C. Birkby. The Mountaineers, complete condition assessment, should be conducted about 1001 SW. Klickitat Way, Seattle, WA 98134. every 5 years, depending on levels of use and a trail’s soil and terrain characteristics. This frequency could be increased if Off Highway Motorcycle & ATV Trails Guidelines for Design, significant environmental values are at risk, but enough time Construction, Maintenance and User Satisfaction. 2d Ed. should pass between assessments to filter out changes due to 1994. Joe Wernex. American Motorcyclist Association, 13515 seasonal effects, weather effects, or the subjectivity of inventory Ya r mouth Dr., Pickerington, OH 43147. Phone: 614–856–1900; crew personnel. The same inventory classification system fax: 614–856–1920, e-mail: [email protected]; Web site: should be employed during each monitoring with key compo- http://www.ama-cycle.org. nents such as trail surface character, trail impact rating, trail drainage, mud-muck index, and track width recorded from Trail Building and Maintenance. 2d Ed. 1981. Robert D. Proud- identical menu selection options. man and Reuben Rajala. Appalachian Mountain Club, 5 Joy St., Boston, MA 02108.

Trail Construction and Maintenance Notebook. 2000. Woody Hesselbarth and Brian Vachowski. Tech. Rep. 0023–2839– MTDC. United States Department of Agriculture, Forest Service, Management Response to Severely Missoula Technology and Development Center, 5785 Hwy. 10 West, Missoula, MT 59808–9361. Degraded Trails

Wetland Trail Design and Construction. 2001. Robert T. Stein- Managing severely degraded trails presents a formidable holtz and Brian Vachowski. Tech. Rep. 0123–2833–MTDC. challenge to resource managers. Severely degraded trails tax United States Department of Agriculture, Forest Service, traditional trail management techniques and sometimes force Missoula Technology and Development Center, 5785 Hwy. managers to investigate and test innovative management 10 West, Missoula, MT 59808–9361. methods, refining them for local conditions. No single set of responses can meet every situation, but a framework can help In addition to these references, supplementary information is guide the process. available from the Missoula Technology and Development Center. Call 406–329–3978 to request the latest list of recre- The trail degradation issue must be addressed on several ation publications and videos. Many of these are available fronts. The National Off-Highway Vehicle Conservation Council through the Federal Highway Administration’s Recreational (NOHVCC), a nonprofit OHV advocacy group, uses an approach Trails Program. To obtain a list of publications and an order they call the Four Es. They are: form, go to Web site: http://www.fhwa.dot.gov/environment/ ➣ ➣ trailpub.htm. Education Engineering ➣ Evaluation ➣ Enforcement Each of these documents provides valuable information on trail design, construction methods, maintenance, or general trail Education is needed to teach users about responsible riding management. While some may be regional in nature or focus and appropriate environmental ethics. In addition, resource on specific types of trails, their basic concepts can be adapted managers and technicians need to be educated about effective to OHV trails. trail management practices. Evaluation is necessary to develop methods to document use, assess impact, and evaluate mitigation methods. Engineering is necessary to develop trail improvement techniques and equipment modifications to reduce Trail Maintenance and Monitoring impacts. Enforcement is necessary to manage use within acceptable impact limits. In many locales, enforcement isn’t a Each trail alignment should receive regular maintenance at viable option. In those areas, enforcement may be implemented least once a year, preferably early in the season of use. as “encouragement,” encouraging users to conduct their Primary activities should include maintaining water-control activities in a sustainable manner. This might best be achieved structures, ditches, and culverts, and clearing fallen timber. 15 Trail Management—Responding to Trail Degradation by providing trail location maps that direct users to sustainable ➣ If yes, what is the cost of stabilizing the existing route com- trails and trail signs that encourage appropriate use. pared to constructing a new trail alignment and rehabilitating the old one? I would also add a fifth E: ‘Enculturation’ (the process of modi- fying human behavior over time). Enculturation can only be In some cases, moving a trail or segment may be an effective accomplished by the steady application of education, appro- method of responding to trail degradation. For example, moving priate evaluation techniques, progressive engineering, appro- a trail from a foot slope to a side slope may significantly reduce priate enforcement, and encouragement. trail wetness. Moving a trail from an open wetland to an adja- cent woodland may stop trail braiding. Figure 7 shows an The five Es show how broadly the issue of degraded trails must example where rerouting should be considered. be addressed. Unfortunately, this report addresses a only a few of the five Es. It is intended as a tool to help educate trail managers and users about OHV trail degradation. In addition, the section on trail condition inventory presents an important evaluation component, and the following section identifies engineering solutions within a range of management options. These options include:

➣ Trail rerouting ➣ Seasonal or type-of-use restrictions ➣ Controlled use (traffic volume restrictions) ➣ Trail hardening ➣ Trail closure

By evaluating these options and developing a forum with users, advocacy groups, and the environmental community, trail managers can resolve many of the conflicts between degraded trails and environmental resources.

Trail Rerouting

Few OHV trails are planned trails where a full range of environ- mental considerations was carefully weighed before construc- tion. In fact, few trails are specifically constructed for OHV use. Most OHV trails developed as individual riders followed game or foot trails or passed through natural corridors to remote fishing, hunting, or cabin sites. In Alaska, many OHV trails develop Figure 7—A heavily used OHV trail in Alaska crosses along routes that originally served as dogsled or snowmobile two distinct soil types. In the foreground, the trail passes through a mixed forest ecosystem where the trails. soils support use along a single track. In the back- ground, the trail crosses degraded wetland soils Because of the unplanned nature of OHV trails, many of them where users have created a braided trail. Managers cross soils and sites poorly suited for the level of use occurring should consider rerouting the trail to stay within the on them today. For example, a trail that originally developed forest system. from a game trail may not be suitable as a primary access route into a heavily used recreation area. A winter route across A rerouting assessment should follow this process: snow-covered wetlands doesn’t necessarily provide a good alignment for a summer OHV route. ➣ Obtain and evaluate aerial photography of the trail alignment.

When numerous segments of a trail have been significantly ➣ Obtain soils data for the area surrounding the trail. Soil sur- degraded by the level of use, trail managers need to ask the vey reports are available from the USDA Natural Resources following questions: Conservation Service.

➣ Do opportunities exist to reroute the trail onto better soils ➣ Conduct a site visit. Take available aerial photography and and terrain? soils data with you. Visit the site during the primary season 16 Trail Management—Responding to Trail Degradation

of use. Evaluate the trail conditions on the ground to identify Table 6—Activities that have the potential to impact trails. relationships between vegetation communities, terrain, soil Impact Use conditions, and trail performance. Table 1 may be of some assistance. Use aerial photographs to identify adjacent areas Generally WINTER, WITH FROZEN GROUND AND ADEQUATE that might support trail use. Identify alternative trail routes slight SNOW COVER: on aerial photographs and flag those routes on the ground. Nonmotorized Motorized (Minimum snow cover (Minimum snow cover 6 inches) 12 inches) ➣ Identify the long-term benefits of the new route compared ➣ to continued use of the existing route. Skiing/snowshoeing Snowmobiling

Dog sledding ➣ Develop a trail design for the alternative route. Develop a detailed construction plan. Identify any stabilization or SUMMER, WELL-THAWED GROUND: reclamation work that is needed on the abandoned trail to Nonmotorized Motorized alignment. Identify methods to redirect use onto the new Hiking Light, tracked vehicles alignment using barriers, markers, or signs. Mountain biking Motorcycle riding

➣ Decisionmakers and environmental groups may object to Horseback riding OHV riding (less than constructing new alignments where existing trails have failed, 1,500 pounds gross so it is important to have photos documenting the difference vehicle weight) between trail segments on degraded sites and trail segments Potentially Unlimited off-highway on more suitable sites. Illustrate the sustainability of the pro- heavy vehicle use posed new location to build consensus for the reroute option.

Seasonal or Type-of-Use Restrictions Controlled Use (Traffic Volume Restrictions)

Seasonal-use restrictions are another option for responding to Controlled use is another management option when responding trail degradation. Because soils are most sensitive to impact to trail degradation. Trail degradation occurs when use exceeds when they are wet, restricting use of sensitive trails during spring the ability of the trail surface to resist impact. Controlling the breakup or periods of high rainfall may significantly reduce trail level of use can be a powerful tool in reducing impacts. Deter- degradation. Also designating winter-season trails that cross mining the appropriate level of use can be difficult, especially wetlands as ‘WINTER ROUTES ONLY’ would significantly since a trail’s resistance to impact can change with weather reduce impacts on sites that are extremely sensitive to impact and type of use. Good decisions require knowledge of existing by motorized vehicles during summer months. trail conditions, patterns and levels of use, and trail condition trends. If trail conditions are stable under existing loads, no Type-of-use restrictions limit the kind of equipment allowed on volume restrictions may be necessary. If trail conditions are trails. For example, restricting gross vehicle weight to less than deteriorating, traffic volume may have to be decreased or trail 1,500 pounds could significantly reduce the size of equipment surfaces may need to be modified to support the increased use. operating on a trail. This would allow managers to build trails to a much lower design specification than when weight is Managing trails through controlled use is complicated because unlimited. there may not be a linear relationship between use levels and impact. Typically, after a certain level of impact is reached, In general, the potential of trail activities to create impacts trails will continue to degrade without any further use. This is ranges from slight to heavy as shown in table 6. clearly the case when vegetation stripping exposes soils to erosion. Finding the balance between appropriate levels of use Reducing the types of use would lessen the potential for impact. and acceptable impacts is a resource management art form, Successfully restricting trail use requires user cooperation ideally backed up with good monitoring of the level of use and and enforcement. Signs, gates, and barriers aren’t enough to resource damage. discourage some users, so public education and development of alternative routes on more resilient trails are needed to Controlled use also requires an authorized and determined encourage compliance. enforcement presence. This may not be readily available. But where it is, monitoring impact and setting the allowable use may be a good management approach to controlling degradation problems.

17 Trail Management—Responding to Trail Degradation

Trail Hardening

Another management option is trail hardening. Trail hardening is a technique of modifying trail surfaces so they will support use without unacceptable environmental impacts to vegetation, soils, hydrology, habitat, or other resource values. Trail hardening should be considered under the following conditions:

➣ Existing trail impacts are causing or are projected to cause unacceptable onsite or offsite impacts, and

➣ More suitable alternative trail locations are not available, or

➣ Alternative trail locations are not environmentally acceptable or economically feasible.

Trail hardening provides the following benefits: Figure 8—This aerial image shows a recently installed section of hardened trail crossing a wetland in southcentral Alaska. The new trail ➣ Defines a single trail alignment for vehicle travel. alignment defines a single route of travel that will prevent the continued development of braided trails. ➣ Stabilizes surface soil conditions along the hardened trail section.

➣ Provides a stable, durable trail surface for OHV traffic. Replacing or Capping Unsuitable Soils—Replacing unsuitable soils is the most intensive, trail-hardening technique. Problem ➣ Halts trail widening and the development of braided trail soils are excavated and removed until a subbase of competent sections. subsoils or gravel has been exposed. High-quality material is placed over the subbase to bring the trail surface up to the ➣ Allows formerly used trail alignments to naturally stabilize trail’s original level. This process is appropriate for trails with and revegetate. a suitable subbase close to the surface and a convenient source of high-quality fill. The work generally requires heavy ➣ May provide for vegetation growth (or regrowth) within the equipment. It is most appropriate near trailheads and along hardened trail surface that helps to reduce visual impacts, highways where heavy equipment can be used to good maximizing site stability and increasing site productivity. advantage.

Trail hardening seeks to improve trail surfaces by one of three Where a suitable subbase is not close to the surface or excava- methods: tion work needs to be minimized, geotextile fabrics may be used to provide a base for surface capping. The use of geotextile ➣ Replacing or capping unsuitable surface soils. materials extends the application of capping to many areas where removal of substandard surface soils is impractical. ➣ Reinforcing or augmenting existing soil structure. Geotextiles, also known as construction fabrics, are widely used ➣ Providing a ‘wear and carry’ surface over unsuitable soils. in roadways, drains, embankments, and landfills. They are constructed of long-lasting synthetic fibers bonded by weaving, The goal of trail hardening is to reinforce soils so they will sup- heat, extrusion, or molding. They come in a wide variety of types port a specified level of use under all environmental conditions. including fabrics, sheets, or three-dimensional materials. They Because of the range of trail-hardening methods available, a can be pervious or impervious to water passage. trail manager must select a method that provides maximum utility for the investment in time, labor, and cost. Utility includes Geotextiles provide four important functions in road and trail site stabilization, resource protection, and suitability for use surface construction: as a surface for OHV traffic (figure 8). ➣ Separation ➣ Reinforcement ➣ Stabilization ➣ Drainage The following section introduces a number of trail-hardening techniques.

18 Trail Management—Responding to Trail Degradation

These functions are illustrated in figures 9a, 9b, and 9c. Geo- textiles work as separation fabrics when they are placed be- Gravel cap with geotextile tween gravel caps and underlying soils to prevent the materials from mixing. The geotextile serves to maintain the original thickness and function of the gravel cap as a load-bearing layer. Geotextiles increase soil stabilization by maintaining the load Shear force contained transfer capability of the gravel cap. This increases effective within gravel cap bearing capacity and prevents subsoil pumping. Geotextiles Ground surface reinforce soils by providing a structure to bond the gravel cap and underlying soils. The geotextile fabric locks the two materials Increased Aggregate stabilization carries load Gravel cap without geotextile Improved Improved drainage drainage

Separation

Geotextile Cross contamination leads to Distributed acts as a soil impacts from shear stress load reinforcement Shear force layer Aggregate Ground surface The addition of a geotextile creates a broad base that cap distributes the load, increasing bearing strength and reducing pumping action. Aggregate migration Figure 9c—Gravel cap with geotextile. Using a geotextile enhances trail performance through separation, stabilization, reinforcement, and drainage.

Upward movement Substandard together and allows the soil to receive a load across a broader of soil soil base footprint. Geotextiles also help maintain the drainage charac- teristics of the gravel cap. In addition to use in trail tread, Figure 9a—Gravel cap without geotextile. The aggregate cap will geotextiles can have important applications in erosion control, lose strength as the gravel is contaminated by the subbase. drainage interception (sheet drains), and ditch liners.

Site conditions such as soil texture, moisture, depth to foun- dation materials, and the type of use indicate when a geotextile Gravel cap with geotextile fabric should be used. Because gravel is difficult and expensive to deliver onsite, the use of a separation fabric makes good economic sense to protect the function of the gravel cap. The use of a geotextile fabric requires adequate capping (a minimum of 6 inches) and regular maintenance to maintain the cap. Regular maintenance prevents the geotextile fabric from being exposed at the surface.

Ground surface Aggregate The National Park Service experimented with the use of geo- cap textile and gravel placement during the summer of 1999 on degraded trail segments of a former mining road connecting Drainage Drainage two administrative sites in the Yukon-Charley Rivers National Separation Preserve (Meyer 1999a). About 678 feet of geotextile with a Geotextile 4- to 6-inch gravel cap was installed over soils in areas that layer crossed melted permafrost soils. Using this technique, the road Substandard soil base alignment was reclaimed as an OHV trail.

Figure 9b—Gravel cap with geotextile. The geotextile layer prevents the migration and contamination of the surface gravel cap by underlying poor-quality soils. 19 Trail Management—Responding to Trail Degradation

Geotextile and gravel placement is relatively simple. The Yukon- Charley approach was adapted from Forest Service methods (Monlux and Vachowski 1995, figure 10). This technique provides a rim structure to minimize the loss of cap material (figures 11 and 12). A local source of suitable gravel was identified. One- half-cubic-yard belly dump trailers, loaded by a skid-steer loader and towed by 4x4 OHVs, transported gravel to trail construction sites.

Adapted geotextile installation

r) te e m ia d s e h c n i 6 o t Geotextile 4 ( Gravel s le o Figure 11—The author installing woven geotextile around a rim log fill p im in the geotextile gravel-capping test installation at the Yukon-Charley R Rivers National Preserve in Alaska. The rim log held the gravel cap on the installation. 6 feet wide

Figure 10—Adapted geotextile installation design.

About 45 labor days and 80 cubic yards of gravel were required to construct 678 linear feet of 6-foot-wide trail, roughly 45 work hours per 100 feet of hardened trail. Construction efficiency dropped considerably when construction sites were more than one-quarter mile from the gravel source because of the small size of the transport vehicles and the round-trip travel time. The loaded trailers, weighing about 2,000 pounds gross vehicle weight, also seriously degraded marginal trail segments along the haul route. Future operations at the site will use larger haul vehicles operating over frozen soils during the winter months.

The geotextile used on the project was AMOCO 2000, a light- grade woven synthetic fabric. The material cost about 5 cents per square foot, quite inexpensive, considering all other costs. Figure 12—A geotextile and gravel-cap installation over permafrost- Overall construction costs for the project were estimated at degraded soils in Yukon-Charley Rivers National Preserve in Alaska. $3.60 per square foot using a labor rate of $18 per hour. Use of geotextile and a gravel cap on this trail allowed the National Park Service to construct a 6-foot-wide OHV trail over a 3- to 4-foot- Cellular Confinement Systems—Cellular Confinement Systems deep muck hole. (CCS) are three-dimensional, web-like materials (figure 13) that provide structural integrity for materials compacted within the cell. They are engineered so cell walls limit the transfer of shear used when constructing shallow-water fords in the contiguous forces within the soil. Employed worldwide for a wide variety 48 States (Forest Service 1987). of uses, cellular confinement systems are a well-accepted soil engineering tool (Ron Abbott 2000). In Alaska, these systems A cellular confinement system consists of a surface-aggregate have been used with success on military runways and remote wear surface, the cell membrane, fill material, and an optional radar sites, Arctic tank farms, construction sites, and boat separation fabric (depending on site characteristics). Fill material ramps (Joseph Neubauer 2000). The systems also have been is usually imported gravel, but onsite material can be used in

20 Trail Management—Responding to Trail Degradation

fill road surface. Spring melt of overflow ice (aufeis), that typically plugs the culverts, scoured fill material out of the web cells each year. Replacing the fill without damaging the cell structure was difficult and time consuming.

Also in Alaska, about 900 feet of cellular confinement systems, with recycled asphalt fill and cap, were installed in 2000 on an access trail in the Turnagain Pass area by the Forest Service (Doug Blanc 2001). Based on the success of that installation, the Forest Service is planning another 3-mile installation adja- cent to a visitor center. Both trails were designed to meet the requirements of the Americans With Disabilities Act and are not representative of remote OHV trails. A more representative installation is a 20-foot test installation at Palmer Hay Flats State Game Refuge (figure 13). Since its installation in August 2000, the trail surface has been performing well, but the capping material has begun to show signs of erosion (Colleen Matt Figure 13—A cellular confinement system being installed on an experi- 2001). mental trail in southcentral Alaska. Four-inch-deep cells were formed by expanding the cellular product accordion style, then backfilling and Cellular confinement systems are manufactured under a variety compacting with a suitable fill material—in this case, sandy gravel. of trade names, including Geoweb, Envirogrid, and TerraCell. The sides of the installation were confined by a 6-inch-deep trench. ➣ Geoweb is available from Presto Plastic Co., phone: 800– 548–3424. some circumstances (the use of onsite fill will be covered later). Installation of the system is labor intensive. The smallest cell ➣ Envirogrid is available from AGH, phone: 713–552–1749. commercially available is 4 inches deep. A minimum of 6 inches of fill material is required to fill the cells and provide a 2-inch ➣ TerraCell is available from WEBTEC, phone: 800–438–0027. wear surface, about 1 cubic yard of loose material per 6 linear feet of a 6-foot-wide trail. While the cell material alone costs Reinforcing or Augmenting Soil Structure—Reinforcing or about 70 to 90 cents per square foot, installation costs include augmenting existing soil structure is a method that adds material the costs of any separation fabric, the fill, cap material, trans- to existing soil to improve its engineering characteristics. Unlike portation of materials, cell panel connectors, and excavation excavating and replacing substandard soils, this method works of a trench or the construction of a curb or rim to confine the with the native in situ soil material. The two major types of materials. material are soil binders and structural additives.

Test installations of cellular confinement systems for trail use Binding agents come in two forms: chemical binders and in the contiguous 48 States have shown mixed results (Jonathan physical binders. Kempff 2000). While the systems provided excellent structural reinforcement for soils, maintaining the surface wear cap to Chemical Binders—The EMC SQUARED system is an example protect the cell membrane has been difficult. Without adequate of a chemical binder. EMC SQUARED is a concentrated liquid curbing, capping material tends to erode from the cell surface. stabilizer formulated to increase the density, cementation, This is particularly true on sloped surfaces. With the loss of moisture resistance, frost-heave resistance, bearing strength, capping material, the cell membrane becomes exposed to shear strength, and stability of compacted earth materials. The damage by trail users. Although such damage usually doesn’t highly concentrated product is diluted in water and applied as significantly affect the cell’s strength, exposed cells are unsightly soil materials are mixed and compacted. The product is activated and create a tripping hazard. by biological catalyst fractions. According to the manufacturer, it is an environmentally friendly product. The system is sup- A somewhat similar problem occurred in the Bureau of Land posedly effective with a wide range of aggregate and recycled Management’s White Mountains District in Alaska. The agency materials, as well as clay and silt soils. reported mixed to poor results using cellular confinement systems on roadways in the Fairbanks area (Randy Goodwin The primary binder in the EMC SQUARED system is Road 2001). Cellular confinement systems were used to cap four Oyl, which has been used extensively as an aggregate binder culvert installations on the Nome Creek road. The systems for resin pavement mixtures. Road Oyl has demonstrated were installed in 50- to 200-foot segments to provide a stable considerable success on urban and accessible trails for the

21 Trail Management—Responding to Trail Degradation

Forest Service, National Park Service, and other governmental Structural Additives—Another method of augmenting an and private organizations. Paul Sandgren, superintendent of existing soil structure is to add a physical component to the the south unit of the Kettle Moraine State Park in southeastern soil body. This can be as an internal structural member or as Wisconsin, reports good success with Road Oyl in binding a surface feature. aggregate-capped mountain bike trails. The park’s south unit, which receives heavy mountain bike use from surrounding Internal Structural Member—The use of cellular confinement urban areas, found annual applications of the binder worked systems to reinforce sandy soils is an example of adding a 3 well in reducing the displacement of a surface cap of ⁄4-inch physical component to an existing soil structure. The original crushed limestone (Paul Sandgren 2001). soil is excavated and used as fill and cap material. The cells of the cellular confinement system add a structural component Test applications of chemical binders in Alaska have proved to the sand that prevents shear force transfer and soil failure. disappointing. The municipality of Anchorage experimented This method was tested by the U.S. Army Corps of Engineers with the use of a chemical binder on an urban access trail with (Webster 1984; Purinton and Harrison 1994) and applied during poor results. The material failed to set up properly. In areas Operation Desert Storm to construct sand roads capable of where the material set up, the surface was very slick. Whether carrying heavy military traffic. The technique has also been the problem was caused by climate or improper installation was applied by an American oil company to build roads through the never resolved (Dave Gardener 2001). Denali National Park Algerian Sahara Desert (Presto 1991). Using a cellular confine- and Preserve has also experimented with a variety of chemical ment system would be an excellent method to stabilize trails binders as dust suppressants on a gravel road that serves as that cross sandy soils. the primary access for the park. To date, results have been disappointing (Ken Karle 2000) Another method used by the Forest Service (Kempff 2000) and recommended by the American Motorcyclist Association (Wernex Chemical binders such as Road Oyl have the greatest potential 1994) is to embed concrete blocks in the body of the soil. The application in urban areas and at trailheads where high-quality concrete block, installed with the block walls in a vertical position, gravel or recycled materials are available. They have yet to be provides a hardened wear surface. The open cell structure of tested on degraded OHV trails in remote locations where the block prevents shear force from being transferred. This unsuitable soil materials, high moisture levels, inability to use method may have applications where blocks can be readily heavy equipment, and severe climatic conditions would present transported to degraded trail sites, but has limited application challenges for this technique. in remote locations. Blocks are available that are specially designed for OHV trails. They are not as thick as normal con- The EMC SQUARED system and Road Oyl are available from struction blocks, and have a different grid pattern. Soil Stabilization Products Company, Inc., of Merced, CA. Phone: 209–383–3296 or 800–523–9992. Other chemical Surface Feature—The geosynthetics industry has developed a binders available on the market include: class of materials known as ‘turf reinforcement’ materials. These products are designed for installation at or near the surface to ➣ Stabilizer (4832 East Indian School Rd., Phoenix, AZ reinforce the surface vegetation mat. The Park Service experi- 85018. Phone: 800–336–2468). mented with one of these materials in a series of test plots established as part of an OHV trail mitigation study conducted ➣ Soil-Sement (Midwest Industrial Supply, Inc., P.O. Box in the Wrangell-St. Elias National Park and Preserve in Alaska. 8431, Canton, OH 44711. Phone: 800–321–0699). In 1996, the Park Service installed four 40-foot test sections of a combination of a drainage mat (Polynet) with a turf ➣ Pennzsuppress D (John Snedden, National Sales Manager, reinforcement mat (Pyramat) over moderately degraded 1 Pennzoil Products Co., 100 Pennzoil Dr., Johnstown, PA OHV trails. Polynet is a ⁄8-inch-thick polyvinyl chloride (PVC) 15909). material, resembling expanded metal decking. Pyramat is a 3 ⁄4-inch-thick, finely woven polypropylene product in a pyramid- Physical Binders—Fine-textured native soil is an example of shaped microweave pattern (figure 14). a physical binder. It can be used where trails are constructed with coarsely textured aggregate or washed gravel. Soil material The manufacturer had extensively tested Pyramat as a soil- containing high sand- and silt-sized fractions is used to fill voids reinforcement product. The company had documented significant between gravel- and cobble-sized material. The fine materials increases in resistance to erosion and shear stress after vege- help “bed” the larger material, reducing displacement, improving tation regrowth (Synthetic Industries 1999). The National Park the quality of the travel surface, and helping vegetation to Service tested both turf reinforcements to see whether they become established. would support existing roots and cushion soil bodies from direct impact. Polynet provided a wear surface, while the open weave of Pyramat allowed for active plant growth and eventually was integrated into the soil surface layer.

22 Trail Management—Responding to Trail Degradation

The products worked fairly well to stabilize trail degradation, but were difficult to install and maintain. They had a poor appear- ance. The material installation cost of the two products was $4 per square foot. It took 26 hours to install 100 linear feet of a 6-foot-wide trail. The full results of the test are detailed in the report, All-Terrain Vehicle (ATV) Trail Mitigation Study: Comparison of Natural and Geosynthetic Materials for Surface Hardening (Allen and others 2000).

Pyramat has also been used to reinforce foot trails and provide erosion control at a portage on Jim Creek, a tributary of the Knik River in the Matanuska Valley near Palmer, AK. Nancy Moore, who works for the Alaska Center for the Environment, coordinated the installation of a 90-foot-long by 8-foot-wide strip of Pyramat at the site in the summer of 2000. The mat was laid on the soil surface, capped with pit-run gravel and topsoil, and seeded to reestablish vegetation. According to Moore, the Figure 14—Polynet over Pyramat was used in this National Park Ser- installation was successful in stemming erosion and improving vice installation to test the addition of a synthetic turf reinforcement trail conditions (Moore 2001). mat. The Polynet, with its more durable wear surface, was installed over the less durable Pyramat. Appendix A identifies the attributes of the Polynet/Pyramat combination and compares the combination with other products tested by the Park Service. While this combination of products The Park Service field tests were encouraging because the may have utility in other applications, it is not considered suitable materials appeared to protect the underlying soils from impact. for hardening OHV trails because of the difficulty of installation They stabilized degradation and provided a durable wear sur- and the limited durability of the wear surface. face for OHV use. Vegetation regrowth on the sites increased from 54-percent cover at installation to 79.5 percent 3 years Providing a Wear-and-Carry Surface Over Unsuitable later (figure 15). On sites with a high percentage of sedge and Soils—The final method of trail hardening is to provide a wear- cotton grass, the materials were well integrated into the root and-carry surface over unsuitable soils. Typically, this is ac- mass by the end of the second year. complished by installing a semirigid structural component on the soil surface that provides a durable wear surface while distributing weight over a broad soil area. In this manner, the material “carries” the weight of the load, rather than directly transferring it to the underlying soil.

The methods of wear-and-carry, trail-hardening techniques for OHV trails discussed in this document include:

➣ Corduroy ➣ Porous pavement panels ➣ Wood matrix ➣ Surface matting ➣ Puncheon

These methods are expensive and labor intensive. It is not practical to use this method to harden the entire length of a trail. It should only be used to harden those segments that cannot be rerouted to more suitable locations or managed to reduce impacts.

Much of the following discussion is drawn from the author’s Figure 15—A Park Service Polynet/Pyramat test installation after 3 personal experience with trail hardening tests conducted in years in a wetland area with a high percentage of sedge. By the third Alaska. This experience includes a formal study conducted in year, sedge had become well established and its roots well entwined Wrangell-St. Elias National Park and Preserve, mentioned in with the Pyramat matting.

23 Trail Management—Responding to Trail Degradation a previous section (Allen and others 2000), data obtained from other test installations, independent research, and conversations with other professionals.

Corduroy—Corduroy has been commonly used to harden trails in Alaska. Many of the first wagon trails in the State were con- structed as corduroy roads. It is not uncommon to see corduroy being excavated during roadwork today. In traditional road con- struction, the corduroy logs were covered with soil or a gravel cap to provide a smooth and durable road surface. Burying the poles beneath the surface cap also served to preserve them. This was especially true when the poles remained water-sat- urated under acidic soil conditions.

For most trail applications, corduroy is not covered with a surface cap. This is primarily due to the scarcity of quality cap material and the expense of hauling the material to installation sites. When corduroy is exposed to the air with frequent wet/dry cycles, its longevity is significantly shorter than if it was buried. Fast- ening the individual poles together is another challenge. Poles can be secured by weaving them with line, spiking them to sill or rail logs, or threading them with rope or cable. Corduroy provides a suitable, if somewhat rough, surface for OHV and foot traffic. Also, woven or threaded corduroy floats on water so it does not provide a stable surface for ponded areas.

The Park Service tested corduroy as one trail-hardening tech- Figure 16—Spruce pole corduroy laid across permafrost soils in Alaska. These poles were imported to the site and secured by nique in the Wrangell-St. Elias study (Allen 2000). Although 3 weaving them with three strands of ⁄8-inch nylon line. corduroy was somewhat labor intensive to install, the expense of installation was mitigated by the low cost of materials. The Wrangell-St. Elias study identified a material installation cost of about $1.75 per square foot. About 25 hours were required to install each 100-foot section of 6-foot-wide trail (figure 16).

Corduroy may also have an environmental cost if trees are harvested in sparsely timbered areas. Three to four poles are required for every linear foot of 6-foot-wide trail. The manage- ment tradeoff of harvesting trees to mitigate trail impacts needs to be evaluated for each installation site. Appropriate thinning methods can mitigate impacts of timber harvesting. Harvesting poles offsite can also mitigate impacts.

Appendix A has more detailed information about the benefits and drawbacks of corduroy. Corduroy is considered a suitable trail-hardening material for relatively short sections of trail when timber is available locally. Figure 17—Wood matrix after installation in the Wrangell-St. Elias National Park and Preserve in Alaska. The wood matrix provided a suitable surface for OHVs, but had several characteristics that Wood Matrix—Wood matrix was another trail-hardening method limited its suitability for future field applications. tested by the Park Service in the Wrangell-St. Elias study (figure 17). The wood matrix was a wooden grid structure constructed of rough-cut, 2- by 4-inch timbers that were notched and fitted The grid formed a rigid unit that had excellent load transfer to form an 8- by 8-inch open grid. The surface of the grid characteristics, but was too inflexible to conform well to terrain. formed the wear surface. The interlocked timbers carried and Although raw materials were cheap, preparing and fitting the distributed the load across the soil surface. The technique was joints was very labor intensive. The green, untreated lumber adapted from an approach developed in Britain (Shae 2000). warped, was difficult to fit together in the field, and was subject

24 Trail Management—Responding to Trail Degradation to breaking at the joints. It was also subject to rot and showed intermittent heavy traffic. In contrast to asphalt or concrete visible signs of deterioration within the first year. pavements, these porous pavement systems reduce surface runoff, increase infiltration, resist erosion, and enhance ground- The installation cost for the wood matrix was $2.90 per square water recharge. foot. About 70 hours were required to install a 100-foot section. The standard industrial installation technique is modified for Additional information on the suitability of wood matrix for trail hardening OHV trails. After surface leveling, the panels are hardening is included in appendix A. Because a wood matrix installed directly over the existing trail surface. The grid cells installation entrapped wildlife in one case, it was removed from are not backfilled unless fill material is readily available. After the Wrangell’s test plots during the second season of the study. installation, the panel’s surface provides a tread surface for That concern and other factors of the material limit its suitability vehicles, and the panel’s structure distributes their weight. The for future trail-hardening applications. open structure of the panels allows vegetation to grow through the panel after installation. On extremely muddy or boggy sites, Puncheon—Constructing puncheon (a type of elevated board- a supplemental geotextile layer may be placed beneath the walk) for wet and muddy footpaths has been a standard con- panels to increase flotation. Polynet PN3000, an open-grid struction technique for many years. Recently, its use in providing drainage mat, has been used for that purpose in a number of a hardened trail surface for ATVs has been pioneered by John test installations in Alaska. Coila, an Alaska homesteader in the Kachemak Bay area of southcentral Alaska. Coila developed an installation similar to One advantage of the panel system is the light weight of the a standard Forest Service design called puncheon with decking panels (about 2 pounds per square foot). The panels do not (figure 18). Coila used locally available beetle-killed spruce and add any significant weight load to wetland surfaces and have a portable bandsaw mill to produce the decking onsite. little impact on surface hydrology. Their use can dramatically reduce the need for culverts or other water transfer structures Typically, Coila cuts timber adjacent to the trail from standing along the trail. or recently fallen, beetle-killed spruce trees. Coila’s slab-plank design uses two size classes of beetle-killed timber. Smaller Two porous pavement panel products have been the subjects diameter timber provides sills and stringers (figure 19). Larger of extensive field testing in Alaska. They are GeoBlock (figure 21) diameter timber provides logs for planking. Sill timbers are 12 and SolGrid (figure 22). feet long and stringer timbers are 24 feet long. The minimum top diameter of logs used for sills and stringers is 7 to 8 inches. GeoBlock is a commercially developed porous pavement system Bark is not typically stripped off the logs, nor are the sill or manufactured by Presto Products of Appleton, WI. GeoBlock stringer logs milled in any fashion. The plank log diameter is has been on the market, in one form or another, since the early controlled by the size the mill can accommodate. Plank logs 1990s and was specifically tested in two earlier configurations are cut to 6-foot lengths to ease handling and are milled into by the Park Service in the Wrangell-St. Elias National Park and 2-inch-thick slabs. Planks are not square edged. All round-faced Preserve. Its primary industrial applications are emergency slabs are discarded. Each plank provides an average of 1 linear vehicle lanes, light service roads, and auxiliary parking areas. foot of boardwalk (figure 20). SolGrid is a commercial porous pavement system developed Coila estimates the expense of the installations at about $5 per by SolPlastics, of Montreal, Canada. SolGrid is a newer product. linear foot, with a construction rate of 50 to 100 feet a day for It has a unique configuration that makes it suitable for irregular a three-person crew when timber is close at hand. Installations terrain and sloped areas. Its primary industrial applications are have been in active service for longer than 15 years with the walkways, bikeways, golf cart paths, and driveways. occasional replacement of a surface plank. An installation guide for the technique has been prepared and is available from the Both products are partially recycled polyethylene plastic panels author (Meyer 2001a). about 39 inches long, 19 inches wide, and 2 inches thick. Geo- 1 Block has also been manufactured as a 1 ⁄4-inch-thick panel. Porous Pavement Panels—Porous pavement panels (PPP) The panels are stabilized with carbon black to help them resist are three-dimensional, structural geotextiles designed to degradation by ultraviolet light. Both GeoBlock and SolGrid are provide a durable wear surface and a load distribution system constructed with an open grid surface and interlocking edges. for driveways, parking areas, fire and utility access lanes, golf The GeoBlock products have a 3- by 3-inch-tall vertical grid 1 cart paths, and approaches to monuments, statues, and reinforced by a base sheet perforated with 2 ⁄4-inch-diameter 3 fountains. The panels are intended to be installed over a pre- holes on a 3 ⁄4-inch spacing. About 44 percent of the base is pared subbase and filled with soil. They are designed to support open. The GeoBlock products form a rigid panel with good grass growth and provide a reinforced turf surface for light or weight transfer between panels.

25 Figure 18—Forest Service Standard Drawing 932-2 of a puncheon with decking boardwalk trail. This design is similar to the one developed by an Alaskan homesteader to provide hardened trails for OHVs. 26 Trail Management—Responding to Trail Degradation

Figure 19—Rough layout of the sill and stringer timbers for puncheon trail construction over a wetland area in southcentral Alaska. Stringers are laid with tops meeting tops and butts meeting butts. Figure 21—A GeoBlock panel. Note the edge tabs used to connect the panels and transfer loads between them.

Figure 22—Two SolGrid panels. Note the U-shaped flex connectors Figure 20—A finished puncheon trail. Note the placement of the between panel subsections. plank taper to accommodate the curves along the trail.

1 1 The SolGrid product has a 2 ⁄2- by 2 ⁄2-inch-tall vertical grid of the SolGrid panels increases their utility on irregular surfaces pattern with an 8- by 8-inch subpanel. When assembled, sub- and on slopes. It also provides an integrated buffer for thermal panels form 16- by 16-inch weight-transfer panels. Flexible expansion and contraction. U-shaped connectors join the subpanels. There is no base 1 sheet. About 85 percent of the grid surface is open for vegeta- In 1996, earlier configurations of GeoBlock 1 ⁄4- and 2-inch tion regrowth. Weight transfer between panels is poor because panels were tested by the Park Service in the Wrangell-St. Elias of the integrated flexible connectors. This can be mitigated trail mitigation study. The test demonstrated that the panels somewhat by the use of supplemental geosynthetics underneath perform very well as trail-hardening materials. They provided the panel. Polynet–PN3000 has been used for that purpose a suitable wear surface for foot and OHV use and were easy in Alaska and has demonstrated some benefit. The flexibility to install. In addition, they readily facilitate vegetation regrowth.

27 Trail Management—Responding to Trail Degradation

Vegetation cover along two hardened trail segments increased Charleston, SC. Sections of the trail had extensive trail braiding on average from 70 to 90 percent and from 48.5 to 77.5 percent due to wet soils. Fifty-five feet of GeoBlock was installed with respectively, within the 4-year study period. a clay-sand fill and a 2-inch cap over a geofabric layer. The installation completely stabilized the soils at the site. More than In 1996, the total installation costs for 100 feet of 6-foot-wide 3,500 passes had been made over the installation by enduro- trail were: type motorcycles within the first 3 months of installation. According to the project manager, not one vehicle has ventured 1 1 ⁄4-inch GeoBlock 2-inch GeoBlock • $6.67 per square foot • $8 per square foot • Installation, 32 hours • Installation, 36 hours • Panel costs with shipping, • Panel costs with shipping, $3.14 per square foot $4.50 per square foot

Since 1996, GeoBlock panel costs have fallen to about $2.15 per square foot for the 2-inch panel, depending on volume. 1 Presto no longer manufactures the 1 ⁄4-inch GeoBlock.

SolGrid costs about $1.60 per square foot, depending on volume. In some areas, SolGrid would require the use of a supplemental geotextile, such as Polynet PN-3000. This would add 15 to 25 cents per square foot to installation costs.

Both products have been tested in Alaska on OHV trails during 2000, 2001, and 2002. In 2000, two 100-foot test sections were installed on a dedicated recreation OHV trail in the Forest Service Starrigaven Recreation Area near Sitka. Several test Figure 23—Test installation of 2-inch GeoBlock at the Palmer Hay Flats sections of GeoBlock and one section of SolGrid were installed State Game Refuge in Alaska. This configuration of panels provided in cooperation with the Alaska Department of Fish and Game at a 4.8-foot-wide trail. Note the interlocking tabs along the panel edges. the Palmer Hay Flats State Game Refuge near Palmer (figures These tabs transfer weight between panels. In this test, GeoBlock was installed over Polynet PN-3000. 23 and 24). The Forest Service reports that the installations were more economical than the standard gravel cap placement and may be applied more widely in the future (LaPalme 2001).

The 2000 test project on the Palmer Hay Flats Game Refuge was successful enough for the department to install an 800- foot section in 2001. That installation included a 600-foot-long shallow underwater section that was supported by a base layer of geogrid and a gravel cap infill to ballast the installation to the pond floor. Also in 2001, the Bureau of Land Management sponsored test installations in the White Mountains National Recreation Area north of Fairbanks, AK, and the Tangle Lakes Archeological District west of Paxson, AK. More than 400 feet of hardened trail was installed at those two sites. In addition, a 300-foot test section was installed in the Caribou Lakes area on the lower Kenai Peninsula in Alaska. Average material costs ranged from $3 to $3.50 per square foot. Among the four sites, trail surfaces were constructed in 4.8-, 6.5-, and 8-foot-wide configurations. Labor requirements varied from 6.5 to 14 hours per 100 square feet, depending on site conditions, logistics, and layout configurations. Figure 24—Test installation of SolGrid at the Palmer Hay Flats State Game Refuge in Alaska. Note the U-shaped flex joints between sub- panel sections. The SolGrid was tested without Polynet PN-3000 to In the contiguous 48 States, GeoBlock was tested on the Wam- test the characteristics of the product when installed on a soft, silty baw Cycle Trail in the Francis Marion National Forest near substrate.

28 Trail Management—Responding to Trail Degradation off of the hardened trail to further impact the wetland site. Except for minor rutting of the surface cap, there has been no noticeable wear to the surface of the GeoBlock panels (Parrish 2001).

Appendix A provides an evaluation of the two products. Geo- Block is highly suitable for use as a trail-hardening material. 1 The 1 ⁄4-inch product, if available, would be suitable for most installation sites, while the 2-inch product could be used for extremely degraded segments, for crossing large ponded areas, and possibly for shallow water fords. SolGrid, which is still undergoing field tests, is suitable for irregular terrain and sloped areas, but is not as suitable for extreme conditions because of its limited ability to transfer lateral loads.

GeoBlock is available from Presto Plastics, Inc., P.O. Box 2399, Figure 25—Safety Deck installed across a tundra surface in Wrangell- Appleton, WI 54913. Phone: 800–548–3424; Web site: http:// St. Elias National Park and Preserve in Alaska. Individual 20- by 20- www.prestogeo.com inch tiles were lashed together with parachute cord and fishnet line. This time-consuming task drove up installation costs. The material SolGrid is available from SolPlastics, 1501 des Futailles St., performed very well on moderately degraded trails and provided an Montreal, PQ, Canada H1N3P. Phone: 888–765–7527; Web excellent surface for most uses. site: http://www.solplastics.com

Appendix B provides an installation guide for these products. Safety Deck was the most expensive material tested in the Wrangell-St. Elias study. Costs were $7.50 per square foot, Matting—Matting is another method of wear-and-carry trail including shipping. Forty-three labor hours were required to hardening. Metal matting was used extensively during World install a 100-foot-long, 6-foot-wide section of trail, for a total War II to reinforce soft soils during airport construction on cost of $5,274 per 100 feet. tropical islands and at remote sites in Alaska. Some of those installations are still in place. The military stopped stocking Appendix A shows the positive attributes of PVC Safety Deck. metal matting in the 1950s and it is no longer manufactured. Although Safety Deck is a strong performer for moderately Its availability as a surplus material is very poor; therefore, it is impacted sites, its high cost limits its use for most OHV trail- not considered a viable material for trail hardening. hardening applications. It may have excellent application on foot or horse trails where the volume of material is much reduced, Matting available in the commercial market today is typically or in providing a surface for accessible trails where the costs plastic decking or industrial antifatigue matting made from PVC might be better justified. or rubber. Plastic decking costs too much for trail hardening and is not discussed further. Rubber and PVC matting are somewhat Safety Deck is no longer commercially available. It was originally more cost effective and are readily available. In contrast to the purchased from The Mat Factory, Inc., of Costa Mesa, CA, rigid porous pavement systems, matting is generally thinner phone: 800–628–7626. The company carries a similar product and more flexible. It drapes across the terrain and provides called Dundee Grass Retention & Erosion Control Mat. That an excellent wear surface, but has a limited ability to transfer product sells for about $5.33 per square foot. Other PVC matting lateral loads. products may also be available.

PVC Matting—Safety Deck was a commercially available PVC Rubber Matting—Rubber antifatigue matting is commonly mat tested in the Wrangell-St. Elias mitigation study. Safety available in discount and hardware supply stores. Rubber mats 3 Deck is a high-density, semirigid, open-grid PVC mat that is are typically available in 3- by 3-foot panels, are ⁄4-inch thick 3 ⁄4-inch thick. It was supplied in 20-inch-square tiles that were and have an interlocking system along their edge (figure 26). laced together with parachute cord (figure 25). Safety Deck was installed on moderately impacted trail surfaces so the Omni Grease-Proof Anti-fatigue Mat (manufactured by Akro need to transfer lateral loads wasn’t too extreme. In this less Corp. of Canton, OH) and Anti-fatigue Mat (manufactured by demanding condition, Safety Deck provided an excellent surface Royal Floor Mats of South Gate, CA) were tested in a prelimi- for all forms of use. However, it was expensive to procure and nary field trial in the spring of 2000 by the National Park Service time consuming to install. Safety Deck had good vegetation and the Alaska Department of Fish and Game at the Palmer regrowth values with an increase from 69 to 91 percent mean Hay Flats State Game Refuge. The mats protected the soil cover over the 4-year study period. surface and conformed well to surface terrain, but provided 29 Trail Management—Responding to Trail Degradation

Appendix A identifies a number of positive attributes of the rubber matting. Rubber matting is not suitable for trail-hardening applications on degraded trails because of its extremely low ability to transfer lateral load. Rubber matting would not prevent shear impacts on wet, finely textured soils. The material may have some limited applications before sites become degraded or could provide a temporary wear surface for special events.

Cost Comparisons for Trail-Hardening Techniques—Table 7 compares installation materials and labor costs for the trail- hardening methods discussed. The costs and hours of labor were developed for data in the Wrangell-St. Elias OHV mitigation study and other Park Service projects. These figures are rough estimates to assist in project scoping. Actual cost and the hours of labor depend on site conditions, logistics, and project design. Figure 26—A section of rubber antifatigue mat undergoing preliminary field trials at the Palmer Hay Flats State Game Refuge in Alaska. The The test installations were small scale. Larger projects would large panels install quickly, but the rubber’s flexibility limits the panels’ benefit from volume discounts on materials and labor efficien- ability to transfer lateral loads. cies. This is especially true when considering shipping costs of raw materials. The unit cost of shipping large quantities of bulky materials, such as the porous pavement products, can no lateral load transfer. The wheel track was noticeably lower be much less than the cost of shipping small quantities. after 10 passes by an OHV on a silty substrate. The low rigidity of the rubber products and their inability to transfer load across Another important consideration is the cost of labor. The figures the mat’s surface limit their application for all but the lightest presented use an $18 per hour labor rate. This represents the of impact areas. cost of a typical government wage-grade seasonal mainte- nance worker in Alaska. The installation of trail-hardening A typical rubber mat sells for about $3.20 per square foot. materials is well suited for summer field crews, such as fire Estimated installation time would be about 14 hours per 100 crews, Student Conservation Association crews, or volunteer linear feet of 6-foot-wide trail. crews. The work is relatively simple and doesn’t require extensive use of power equipment. Fire crews filling in between fire calls or seeking early season training would be excellent sources of labor. The availability of cheaper labor could significantly reduce installation costs.

30 Trail Management—Responding to Trail Degradation

Table 7—Materials and labor costs of different trail-hardening methods.

Hours to Labor costs Installation Installation Cost per Cost per install per per 100 linear cost per cost per square 100 linear 100 linear feet1 at $18 square 100 linear Material foot ($) feet1 ($) feet1 per hour foot ($) feet1 ($)

Corduroy 1.00 600 25 450 1.75 1,050 Wood matrix 0.80 480 70 1,260 2.90 1,740 Onsite puncheon 0.83 500 24 432 1.55 932 Gravel/geotextile 2.25+2 1,350+2 45 810 3.60+2 2,160+2 1 GeoBlock, 1 ⁄4 inch 2.75 1,650 38 684 3.89 2,334 GeoBlock, 2 inch 3.50 2,100 40 720 4.70 2,820 SolGrid 2.25 1,350 40 720 3.45 2,070 PVC matting 7.50 4,500 43 774 8.79 5,274 Rubber matting 3.50 2,100 14 252 3.92 2,352

1 Trails are 6 feet wide. 2 Depends on gravel source and haul distance.

Trail Closure limitations that may restrict implementation of alternatives should be discussed. User groups may offer to accept some The final management option to be discussed is trail closure. of the responsibility of maintaining or implementing necessary As a last resort, resource managers may close a trail to protect trail improvements to avoid losing access. threatened resources. This would halt direct trail impacts, but might not halt secondary impacts, such as erosion and sedi- In the contiguous 48 States, user advocacy groups such as the mentation. A trail identified for closure needs to be assessed American Motorcyclist Association and National Off-Highway and stabilized or reclaimed as necessary. Vehicle Conservation Council have often been able to help facil- itate projects that protect trail access while assuring resource Closing a trail is seldom popular with trail users. Before the protection. These on-the-ground projects have rallied a large action is taken, the proposed closure should be discussed at response from volunteer groups and individuals who develop a public forum. Alternatives to the closure—such as reroute a certain “ownership” of the trail resources they are working options, seasonal or type-of-use restrictions, controlled use, to protect. Often the energy generated by a resource conflict trail hardening, or other surface improvements—should be has been harnessed by land management agencies to addressed and evaluated. Agency budgetary and workforce generate support for work that has prevented trail closure.

31